Optical imaging, especially in the near-infrared (NIR) wavelengths, is expected to have significant impact for in vivo imaging because of the low absorption of biological molecules, high sensitivity, high spatial and temporal resolution, safety, and low costs.
The resolution of optical imaging relies greatly on the stable, highly specific and sensitive fluorescence probes or dyes. Indocyanine green (commonly known as ICG) is an FDA approved fluorescence dye for use in coronary angiography, evaluation or hepatic function and monitoring blood flow. However, ICG has a very short plasma half-life, thus limiting the imaging time available during its vascular circulation. The use of polymeric and metallic nanoparticle-based fluorescence probes for optical imaging demonstrated enhanced resolution and prolonged half-life in plasma. However, the toxicity of these nanoparticle-based probes is a concern due to the presence of synthetic polymers or toxic metals (S. Keereweer et al., Optical image-guided surgery: where do we stand? Mol. Imaging Biol. 2011, 13, 199-207.)
There is still a need for a more effective and safe fluorescence probe for optical imaging of the vasculature and/or the lymphatic system. The present invention addresses this need.